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Guys,
One of the things I see missing from your discussion is how much the tanks
buoyancy changes from full to empty. Look at the abyss tank chart and you
will see the PST 104 has a change of 4.6 lbs vs. 5.9 lbs. for the Luxfer 80
(77), now double those numbers and look at the weight difference needed.

http://www.abysmal.com/pages/features-cylinders.html

Also from looking at this chart I'd say that the Luxfer 80's are going to
start swinging positively buoyant closer to 2000 psi than 1100 psi. A
doubles manifold may push it down some but not that much.

DT



>
>
> Don Burke wrote:
>
> > From: Marv <ajmarve@ba*.ne*>
> >
> >> ok
> >> first, if you read Pauls post you should have been able to infer that
he
> >> was discussing the weight of the tanks on dry land.
> >
> >
> > The _only_ place that is true is on dry land.
>
> um, ok?
>
>
> >   For a given gas capacity, a
> > diver wearing aluminum tanks is a bit heavier on the boat since the
> > displacement of the aluminum requires wearing more weight.
>
>
> only if you breathe the tanks below approx 1100psi, the point at which
> they swing positive.
>
> >
> >
> >> If you ever tried to lift a set of 104s and then right away move a set
> >> of 80's, like i do when im filling in my garage, you would see the
> >> difference between the two,
> >
> >
> > That's comparing apples and watermelons.
>
> Thats what i was saying, that the tanks were different. So much so that
> if dry land weight was a consideration, as Paul indicated in his
> original post, then the 80s "beat" the 104's. i never mentioned steel
> 80's and esp not hp 80s like the pst. There is no reason to bring them
> into the discussion in fact because they swim horribly. you guys can
> talk numbers all you want, try diving the tanks and then tell me about it.
>
> > I made up a set of AL 80s and I'm wearing 11# of lead (with a steel
plate)
> > with a wetsuit in fresh water.  I haven't hit the ocean with these yet,
so
> > my calculation of 17# is approximate at best.  As soon as I go dry,
those
> > tanks will become deco/stage/rec bottles.  If I didn't already own the
AL
> > 80s, I certainly wouldn't have bought them.
> >
> > Those 104s are a pretty heavy item as steel tanks go.  They weigh about
the
> > same as an OMS 125.
> >
> > Capt JT wears a set of 104s and more power to him.  I haven't asked him
what
> > he like about them.
> > I have a welder and a generator I can lift when I feel the need for a
> > hernia. :)
> > I think I'll go for 112s when I get to that.
>
> the 104 is a  good choice for cave, where extra buoyancy is a minus. one
> can manage to dive them in the ocean,but i dont see them as ideal in the
> ocean.
>
> > The wall thickness on an aluminum tank is so much greater than that of a
> > steel tank, the weight of the tank is more and the displacement is more.
>
> and in the water you have the wt of the valve, the gas, the reg to
> consider, along w/ all you other gear.
>
> Marv
>
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